The invention relates to a weld stud for drawn-arc stud welding.
In the case of drawn-arc stud welding, a metal stud is welded onto a component. For this purpose, an arc is ignited between the face surface of the stud and the component. The stud is initially placed onto the component, and a pilot current is activated. By virtue of the metal stud being lifted slightly from the component, the arc is drawn. The two parts are melted, and are joined together by the exertion of a light pressure.
Weld studs for drawn-arc stud welding normally have a functional section, which in the welded state permits the fastening of components or parts, and a welding section, by way of which the weld studs are welded to a component. The welding section is intended for being at least partially melted during the welding process and for entering into a cohesive connection with the component.
FIG. 1 shows a conventional weld stud 1 for drawn-arc stud welding. The welding section 2 is of conical form with a shell surface 3 and has, at its free end, a face surface 4 in the form of a shallow frustum, which ends in a planar section 5. The face surface 4 thus has two edges: a first edge K1, which delimits the planar section 5, and a second edge K2 at the transition between face surface 4 and shell surface 3. For the welding, the weld stud 1 is, by way of the planar section 5 of the face surface 4, firstly placed onto the component and then removed therefrom, whereby the arc is ignited between component and face surface 4.
With this form of stud, it is however often possible to realize only inadequate quality of the welded connection. In the welding region, defects arise as a result of non-uniform, unilateral melting of the welding flange, or non-uniform melting of the component occurs. As a result, the weld seam that is formed is uneven, resulting in oblique positioning of the stud. Furthermore, for example if too much welding energy is used, evaporation of the material situated in the marginal region of the face surface occurs, whereby the strength of the joining connection is no longer ensured.
The invention is therefore based on the object of providing a weld stud by way of which, even with non-optimum configuration of the welding parameters, uniform melting can be realized, and improved quality of the welded connection can be achieved.
These and other objects are achieved by way of a weld stud according to the invention for drawn-arc stud welding, which weld stud has a functional section and a welding section. The welding section forms an end of the weld stud and is delimited by a face surface which is domed outwardly in the longitudinal direction of the weld stud.
The invention is based on the realization that, through the formation of a face surface with an outwardly domed form, the tendency of the arc to run along the edge of the stud face surface can be counteracted. Owing to the convex form of the face surface, the arc does not migrate to a particular position, whereby the uniformity of the melting can be considerably increased.
The functional section of the weld stud serves for the fastening of a component or of a part and may be formed with an external or internal thread or may take on other forms suitable for the intended function, such as, for example, a hook, an eyelet, one or more pins, etc.
The welding section is that section of the weld stud which, during the welding, is at least partially melted and enters into a cohesive connection with the component.
In a preferred embodiment, the face surface is of rotationally symmetrical form with respect to a longitudinal axis of the weld stud and, in particular, has the shape of a spherical segment, of a segment of an ellipsoid or of a segment of an elliptical paraboloid.
Particularly uniform melting can be achieved if the face surface has, in the longitudinal direction of the weld stud, a dome height of at least 1.5 mm or more and, in particular, of 2 mm and more.
In one refinement, the uniformity of the melting may be further increased by virtue of the face surface transitioning in continuous fashion, without an edge, into a side surface which delimits the welding section, that is to say the face surface and side surface have a common tangent at their common boundary.
In a preferred refinement, the face surface adjoins a conical section whose diameter widens, proceeding from the diameter of the face surface, with increasing distance from the face surface.
To increase the overall strength, the face surface may, in the case of a weld stud whose functional section has a thread, have a diameter which is at least as large as the core diameter of the thread.
The weld stud may preferably be manufactured in one piece, or the welding section and the functional section may be composed of different materials and cohesively connected to one another. In one refinement, the weld stud is manufactured in one piece from an aluminum alloy.
The weld stud described above may be used in particular for drawn-arc stud welding on a vehicle body, on chassis components or in the field of battery or accumulator technology (e.g. high-voltage batteries). The weld stud according to the invention leads to more constant quality of the stud welds with fewer failures, and is not sensitive to process disruptions.
The above-described characteristics, features and advantages of this invention, and the manner in which these are achieved, will become clearer and better understandable in conjunction with the following description of the exemplary embodiments. Where the expression “may be” is used in this application, this represents both the technical possibility and the actual technical implementation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.